In the currently ongoing work of standardizing the long-term evolution (LTE) concept in 3GPP there have been numerous contributions on methods related to inter-cell interference coordination (ICIC).
Within the 3GPP working group RAN1 there has been a decision that the transmission of an “overload indicator” (OI) over the X2 interface (between base stations or eNodeBs) will be supported for the purpose of coordinating the interference between cells. No decisions have yet been taken on what this OI shall actually contain and how it should be used. The OI could be anything from a single bit to several bits per OFDM resource block. The transmission of the OI could be periodic or triggered by different events. In fact, it is not necessary that all aspects of the usage of the OI and the actual content of the OI (number of bits, information elements, etc) are subject to standardization.
Inter-cell interference management and inter-cell interference coordination has a vast literature, since the problem space is well known from, for instance, other cellular technologies, including GSM and EDGE. However, there is no distributed algorithm presented whose aim is to maximize overall throughput by avoiding collisions in a dynamic fashion. Semi-distributed algorithms for coordinated power and channel allocation have been proposed in the literature, see for instance [3][4].
Distributed algorithms for power control and interference management are well known. The scope of prior art does not easily extend to a multi-cell environment in which no central entity exists.
Multi-cell radio resource management in general and multi-cell interference management in particular also has a rich literature, although significantly less works have been done than for single cell systems. However, none of these works focus on what should be communicated between base stations in an orthogonal multi-cell system such that overall throughput approaches a near-optimal value. In fact, none of these algorithms focus on the case of distributed base stations and the communication between them.
The issue of dynamic distributed multi-cell interference management is well known and extensively discussed. However, apart from the overload indicator proposal, there has not been a specific proposal on X2 messages that have the goal to minimize the impact of interference caused by the different cells to one another. This is despite the fact that it has been indicated that such X2 message exchange is expected to enhance the overall system performance, see for example [1].
From a system development and from a standardization perspective, it is important to specify what messages between the base-stations should be communicated such that inter-cell interference management is efficiently achieved, see [5]. In fact, from that perspective, the actual inter-base station messages and (and how the contents of such messages can be constructed by the participating base stations) are more important than the algorithm that resides in each base station and dictates what the base station should do upon the receipt of such messages.